GC MS DETERMINATION OF METHADONE IN URINE AND PLASMA FROM PATIENTS UNDER DETOXIFICATION TREATMENT/

A gas chromatography-mass spectrometry (GC-MS) method for determining methadone in urine and plasma by liquid-liquid extraction with proadif en as internal standard is proposed. The linear concentration range is 0.05-10 mu g/mL for urine and 0.05-1 mu g/mL for plasma, and correlat ion coefficients are quite good. The mean recoveries achieved are 64.3 0% from mine and 79.03% from plasma, with a coefficient of variation l ess than 1.25%. Samples from patients under a detoxification treatment involving administration of daily doses of 20-200 mg of methadone exh ibited concentrations of this drug over the ranges 0.10-13.25 mu g/mL (urine) and 0.07-0.42 mu g/mL (plasma), which confirm that it is excre ted largely via urine.